Usefulness of high-frequency analysis of signal-averaged surface electrocardiograms in acute myocardial infarction before and after coronary thrombolysis for assessing coronary reperfusion.

The incidence of late potentials on the signal-averaged electrocardiogram before and after coronary thrombolysis was studied in 54 patients with an acute myocardial infarction of less than or equal to 5 hours' duration and with an angiographically documented total occlusion of the infarct-related coronary artery on admission. A significant (p = 0.038) 50% relative reduction in the incidence of late potentials was observed in the group of 35 patients who underwent reperfusion: from 16 of 35 (46%) before to 8 of 35 (23%) at 120 minutes after the start of thrombolytic treatment. No significant reduction was seen in the 19 patients in whom thrombolysis was unsuccessful: from 8 of 19 (42%) before to 7 of 19 (37%) afterward. Despite successful recanalization, late potentials persisted or newly developed after thrombolytic therapy in 8 of 54 patients (15%). It is concluded that successful thrombolysis reduces the incidence of late potentials on the signal-averaged electrocardiogram but that the sensitivity and specificity of this finding are not high enough to allow reliable monitoring of coronary reperfusion at the bedside.

[Late potentials in patients with myocardial infarction subjected to coronary thrombolysis]. / Comportamento dos potenciais tardios em portadores de infarto do miocárdio submetidos à trombólise coronária.

PURPOSE: Analyse the behavior of the late potentials (LP) in patients submitted to thrombolysis with success. MATERIAL AND METHODS: Thirty-five patients with acute myocardial infarction, 32 (91.4%) male with ages varying from 33 to 68 (mean 52.6). Thrombolysis was obtained during cinecoronarography with intravenous infusion "in bolus" of doses of 50 mg, 60 mg and 70 mg of rt-PA, with a new bolus of 30 mg at 60 minutes after the procedure. A new angiographic study was performed 12-48 hours late. The high resolution ECG was taken with the ART system model 1200 EPX, before, after and 72 hours later. The presence of electrical activity in the last 40 ms of the QRS complex with less than 20 mu volts in amplitude and more than 35 ms in duration characterized the LP. RESULTS: LP was observed in 16 (46%) patients during the phase of arterial occlusion. LP was recorded only in 23% after recanalization and in 26% when the infarcted related artery (IRA) remain opened. The reduction in the LP was 43.5%. Only one patient with LP had threatening arrhythmia. CONCLUSION: In patients with demonstrated thrombotic occlusion of the IRA, the recanalization diminished the incidence of LP in 43.5% of the patients. Further studies are necessary to achieve the exact clinical importance of these findings.